Some large work machines include elevated cabs accessible only by an access system, such as a stairway or a ladder. Some of these ladders are disposed vertically on the side of the work machine. A vertical ladder only slightly increases the overall footprint of the work machine, and can be secured in a location not susceptible to contact with obstacles, such as piles of materials, mine walls, or other obstacles. However, vertical ladders also have some drawbacks if used improperly. For example, some operators may not grip the ladder with both hands when ascending or descending because they may carry objects up and down the ladder. In addition, many work machines have a door to an operator's cab at the top of the vertical ladder. In such a situation, the operator may be required to balance himself on the vertical ladder, while reaching for the door handle. Furthermore, some doors swing outwardly over the ladder. In these instances, the operator may be required to move his body on the ladder out of the path of the door when opening the door. This can be difficult to do while holding onto the vertical ladder.
To make this easier, other work machines include inclined ladders or stairs extending from the work machine toward the ground. The inclined ladders and stairs generally do not require that the operator use both hands to balance himself. Accordingly, inclined ladders and stairs increase the stability of the operator when ascending or descending, providing easier access to the operator's cab. However, like vertical ladders, inclined ladders and stairs have some drawbacks. For example, inclined ladders or stairs typically extend away from the body of the work machine, increasing the overall footprint of the work machine. Accordingly, the inclined ladder and stairs are more susceptible to crashing into objects, walls, and materials and becoming damaged.
One system for providing a stairway for an on-highway truck is disclosed in U.S. Pat. No. 6,264,222 to Johnston et al. The '222 patent discloses a retractable stairway assembly that is pivoted between a deployed and a stowed position. The retractable stairway rotates about the pivot point in a horizontal direction from a location below the vehicle cab to a position on the exterior of the vehicle cab. However, the system in the '222 patent is not self contained, not easily retrofit to existing machines, and may require additional control in order to operate the stairway assembly.
The access system disclosed herein overcomes one or more of the shortcomings found in systems in the prior art.